Most teachers develop a bond with students when they achieve great things together, as we did at a tournament in 2000.

Fellow taiji instructor Kim Ivy of Seattle put an interesting post on Facebook last week and it triggered some thoughts that probably all instructors entertain from time to time.

It's a bit puzzling to us, and it actually sometimes hurts a little bit when we spend time with a student, coach them, laugh with them, give time and energy and care, only to have them suddenly vanish and we never hear from them again.

It has happened to me several times. I have had students who achieved rank, attended tournaments with me and we had a great time, developed a camaraderie, and suddenly they are gone and never communicate, as if I was just some passing acquaintance.

As a student, I left one or two teachers without saying anything, including my very first teacher, Sin The. But in all the time I was a student of Sin The's, rising to 3rd degree brown belt, I can't recall one conversation that he ever had with me. I'm not even sure he ever gave me any personal coaching at all. It was a very impersonal environment, and between my youth and the lack of a relationship with the teacher, I simply left the school. It probably was not the right thing to do.

So what is the best way to leave a martial arts teacher? When is it appropriate to leave without a trace?

Students leave for a variety of reasons -- they may simply not have the money for the monthly fee; they might be bogged down with school, with jobs, with personal relationships or family. All that is understandable, and all teachers understand that life often gets in the way of martial arts.

Personal integrity is important here. If your teacher has displayed integrity in his or her dealings with you -- if the instructor has been honest and friendly and put forth an effort to teach you skills -- you will show integrity by communicating in person when it is time to leave the school. 

However, if the teacher has allowed or created a negative or hostile environment in the school, or has been personally and unreasonably critical, it might be best to simply walk away.

If you find that your teacher has lied about his or her background, if they have made up their history or if they have lied about their lineage or teachers, will it do any good to confront them on it? Probably not. Would it be honest to let them know you are disappointed that they lied? Yes. But I could understand it if a student simply left, because again, the issue of personal integrity has come into play. If the teacher shows a lack of personal integrity by lying, the student does not owe him anything but contempt, in my opinion. Taking money under false pretenses is stealing.

If you have even the slightest feeling that your teacher could become angry or abusive if you tell him that you are leaving, it is best not to say anything. Just leave.

In the end, you should do what you think is the right thing to do, not the easy thing to do. It's always easiest to just walk away from any relationship. Some people break up with girlfriends or boyfriends with a text message. That's pretty cold. Someone who has meant something to you deserves a face-to-face conversation unless abuse or physical violence is a possibility.

Personal integrity is not always the easy route, but it is always the most satisfying in the end. And if you are studying martial arts, isn't integrity one of the core strengths that the art is supposed to help you develop? You can demonstrate your internal strength by doing the right thing.

Nancy and I went to an Asian restaurant in Davenport, Iowa on Saturday evening and were seated in a room all to ourselves. The waitress started a small fireplace. It was very relaxing.

And then I realized that if a terrorist with a gun walked into the door of the restaurant, we were sitting ducks. There was no escape.

What a shame that we live in a world where this is something we think about at a time when we should be simply relaxing and enjoying ourselves.

The terrorist attacks in Paris this weekend hit a lot of us in the civilized world like a sidekick to the stomach. Many of us watched news reports from the restaurants and concert hall with the same thoughts -- what if we had been there when gunmen walked in? How do we protect ourselves against a terrorist attack?

I do not carry a gun. I don't even own a gun. Nancy and I have considered buying one to keep in the house, but I have always resisted the "concealed carry" idea. All we need in a world of hair-trigger tempers and road rage is a population of frustrated people carrying firearms.

And yet, self-defense has been my hobby since 1973. What good is self-defense in an age of terrorism?

For decades, I have endured comments such as, "You know kung-fu? I'll shoot you before you can use your kung-fu. I know Smith & Wesson."

That's a silly comment, because studies have shown that if you have a gun on you, a motivated attacker will be on top of you before you can pull the gun. And besides, you don't have to worry about defending yourself against a guy who practices kung-fu. You have to worry about the criminal who wants to kill you -- right now. He isn't messing around and he is not going to warn you in time to pull your gun.

On the other hand, you can spend decades working on empty-hand self-defense techniques only to be blown away by a radical jihadist with an assault weapon because you were seated in the wrong part of a restaurant.

None of us want to be paranoid. It is not healthy to constantly feel the urge to look over your shoulder. We must be able to relax. But we must also expect the unexpected.

And so here are a few things you can begin doing as a safety precaution:

• Always scope out the exits. Know an escape route if you need one.
• If possible, request a restaurant table near an escape route -- an exit or near the kitchen -- away from the front door.
• Sit so that your back is not to the door. Sit so that you have a view of what is happening.
• In a public place such as a mall, be mindful of who is around you and where the exits are located. When you enter a store, be aware of exits into the back rooms. Those exits sometimes lead to the outside or into another hallway, or there may be storage areas where you can hide.
• Some people say if you are in a store and employees start running in a particular direction, follow them because they may have practiced an emergency exit drill.
• Movie theaters are difficult because if you sit in the main part of the theater, and an attacker with a gun walks in, you are typically a sitting duck. One possibility is to sit closer to the exits, which are often next to the screen. In older theaters, there were also exits at the top of the stairs, but most theaters now are built differently and there is no exit at the top.
• Most importantly -- Remain Mindful and alert to what is happening around you. This does not mean to remain in a hyper-vigilant "fight or flight" mode all the time. It means to pay attention to people, sounds, and the atmosphere around you. 

I have written about an incident that happened in Chicago a couple of years ago. Nancy and I were walking along the shops on Michigan Avenue when the crowd of people on the sidewalks and in the stores began getting larger. There were more young people and I noticed that their voices were growing louder as they talked and laughed.

After a few minutes, I realized that something did not feel right to me.

"Let's go back in the opposite direction," I said, and I held Nancy's hand and guided her away from the shopping area, back toward our hotel.

"What's the matter?" she asked.

"My self-defense radar went off," I said. "Something isn't right."

We got clear of the crowds and stopped for dinner, then returned to our hotel room in time to turn on the 10:00 news. The lead story told of how bands of young people had started running through the crowds attacking shoppers on Michigan Avenue at exactly the location we were shopping. It had started just a few minutes after my "Self-Defense Radar" had pinged. 

Nancy was impressed. She had not noticed anything, but I had remained mindful, aware of what was happening around me. It was not anything I had been doing consciously -- I was just being mindful as I normally am.

As I was reminded that night in Chicago, the best self-defense is to not be there in the first place. If you know of a bar where fights sometimes happen, stay away from that bar. If you are walking down the street and see some people hanging out that give you a bad vibe, cross the street or -- better yet -- turn and go the opposite way. Being a little inconvenienced is much better than being attacked.

I live in the Quad Cities, on the border of Iowa and Illinois. This is a pretty safe place compared to many American cities. But all you need is one mentally ill loner, or a radical young man or woman who decides to align their goals with ISIS and you can find yourself among others who say, "We never thought it would happen here."

But we cannot remain locked in our homes. We cannot be afraid to go out. If we are afraid, the terrorists achieve one of their goals -- to terrorize. So relax, breathe deeply, remain centered, enjoy your life, but remain mindful at all times.

I love the Internet. It allows me to engage with martial artists worldwide.

Today, I received a very nice email from a Tai Chi enthusiast in Denmark. He writes: